Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753082Ab3GFKu6 (ORCPT ); Sat, 6 Jul 2013 06:50:58 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40779 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752827Ab3GFKu5 (ORCPT ); Sat, 6 Jul 2013 06:50:57 -0400 Date: Sat, 6 Jul 2013 12:50:10 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Frederic Weisbecker , Alex Shi , hpa@linux.intel.com, tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, andi.kleen@intel.com, mingo@elte.hu Subject: Re: [URGENT rfc patch 0/3] tsc clocksource bug fix Message-ID: <20130706105010.GV18898@dyad.programming.kicks-ass.net> References: <1372916056-24301-1-git-send-email-alex.shi@intel.com> <20130704075840.GH18898@dyad.programming.kicks-ass.net> <20130705143833.GT23916@twins.programming.kicks-ass.net> <20130705212235.GU23916@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1411 Lines: 34 On Fri, Jul 05, 2013 at 11:50:05PM +0200, Thomas Gleixner wrote: > On Fri, 5 Jul 2013, Peter Zijlstra wrote: > > On Fri, Jul 05, 2013 at 05:24:09PM +0200, Thomas Gleixner wrote: > > > See arch/x86/kernel/tsc.c > > > > > > We disable the watchdog for the TSC when tsc_clocksource_reliable is > > > set. > > > > > > tsc_clocksource_reliable is set when: > > > > > > - you add tsc=reliable to the kernel command line > > > > Ah, I didn't know about that one, useful. > > > > > - boot_cpu_has(X86_FEATURE_TSC_RELIABLE) > > > > > > X86_FEATURE_TSC_RELIABLE is a software flag, set by vmware and > > > moorsetown. So all other machines keep the watchdog enabled. > > > > Right.. I knew it was enabled on my machines even though they normally > > have usable TSC. > > Yeah, but our well justified paranoia still prevents us from trusting > these CPU flags. Maybe some day BIOS is going to be replaced by > something useful. You know: Hope springs eternal.... Oh quite agreed. Its just that at several times I've wanted to disable the thing. Now I know you can do using the kernel cmdline. Previously I had to wreck code -- not that much harder really :-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/